Steve Bennett

What things can cause lost link communications between remote and drone?

Recommended Posts

I understand very basic things about interference but haven't seen a comprehensive list of things that can cause this to happen. I'm not willing to experiment either. :) 

Obvious things are cell towers/radio towers, high tension power lines and large metallic objects. What else?

I recently heard someone say that large container ship to shore radios can cause a loss link. Can anyone confirm/explain?

Share this post


Link to post
Share on other sites

In my opinion, the biggest culprit here is wi-fi networks.  They typically operate in the 2.4 Ghz and 5 Ghz ranges. (BTW - so does your microwave oven). That's where Drones like DJI's operate.  There are many idiots in the States who feel it's their right to use as much transmit power as they can find in spite of FCC regulations.  Citizens Band and other 2 way radio services fall victim to this regularly but FCC regulates this as best they can.  So, let's assume you are operating near a large apartment building with a  lot of tenants with wi-fi systems inside.  Even though those modems and routers are low power, they can still pose a problem.  I seriously doubt that container ships, which use marine VHF when in close to shore (150-160 Mhz roughly) would have any influence on sUAV's.

Share this post


Link to post
Share on other sites

I came across this post specifically because I was searching for some more information after I had a brief lost link incident (about 30 seconds) as I was flying right as a cargo ship passed us. We had already been flying for over 30 minutes without incident when this happened, and the cargo ship adjacent to us was the only visible environmental difference. I am not 100% positive the cargo ship was the cause of the lost link, but I sure as heck will be landing next time I see one headed for us, just in case.

Share this post


Link to post
Share on other sites

Most communication to drones is line-of-sight, so if you could see the drone generally you can communicate with it.  Also, ships have both passive and active radar, most active radars are medium and long wave devices that will overpower the short wave 2.4 and 5.8.

Fortunately radars have a “narrow” focus so communication will usually be reestablished once the ship passes by and the drone is nolonger in that narrow band.  What the drone drone does when this happens depends on how your failsafe is set.   

Keep in mind that ocean going vessels have to “see” to the horizon, if they’re close to land they generally don’t need them unless navigating in limited visibility like fog. So it can also depend on where you are when you encounter them.  

Share this post


Link to post
Share on other sites

Another possibility is multi-path interference.  Not sure how close you were to the ship, but that massive steel vessel could be reflecting the signal from the transmitter to the drone.  If that were the case, the drone could be getting the same instructions a few milliseconds apart.  Back in the days of analog TV ( just a few years ago) this would be a typical cause of ghosted images - steel buildings, bridges, and even mountains. 

Share this post


Link to post
Share on other sites
10 hours ago, Av8Chuck said:

Certainly could be an issue but we take off and land on large ships without that issue.   

I'm no radio expert but operating from would seem to be a different dynamic than operating near.  Dunno.

Share this post


Link to post
Share on other sites

@Dave Pitman is absolutely correct here. Now I'm not sure that multipath had anything to do with the original problem, but Dave's point is well taken.  There would be no perceptible delay to the receiver when operating from on board the vessel plus any reflections from some part of the vessel.  On the other hand, If the transmitter was, let's say 1000ft from the ship and 1000 ft from the receiver (in a different direction) there could be a delay and it might be a problem.  However, I have no idea whatsoever as to filtering in these units and whether they can eliminate this type of interference.

Share this post


Link to post
Share on other sites

@Steve Bennett I think one of the most under the radar culprits for loss links is overheating of the monitor devices (phone or tablet). One of the surveying/engineering drone companies I work for makes it very clear to keep all of our devices cooled down. And it usually keeps down chronic loss links. Also, There have been times when I had a very hot device and could not see the screen at all. So no scientific evidence for this question just going off of pure experience. 

Share this post


Link to post
Share on other sites

I was flying my DJI Mavic 2 Pro off a fishing boat in the Louisiana marsh last week. Three trips up, three 'lost connections.' Very freaky.

We noticed that the trolling motor--which has its own wifi/remote setup--seemed to be affected when the drone was up. So I tried going

up with the trolling motor stuff turned off BUT IT STILL HAPPENED. I didn't lose the drone but if I hadn't had LOS, it might have been a huge issue.

Afterwards, I read that the GoPro wifi signal can sometimes interfere with other operations. There WAS a GoPro running this whole time.

Anybody know if this could have caused it? This was really unsettling as I've had no issues flying this machine for the past year.

Share this post


Link to post
Share on other sites

Did the fishing boat have a radar?

The GoPro BT usually only effected the Phantom 2's when it was mounted on the drone.

Share this post


Link to post
Share on other sites

Yes, the boat had a modern Lawrence fish finder/mapping device on it. I didn't think to try having them turn that off. Maybe

that was the culprit? Also I plan to take my GoPro, get it running and see if it creates any interference for me with the Mavic controller.

Share this post


Link to post
Share on other sites

 

In August last year, we took a cruise to Okinawa. When a friend mentioned the mission, he repeatedly stressed that he should not fly on the cruise. I was prepared to fly. I asked him why he happened to have a friend on a cruise. Playing, the two planes flying all went out of the sea. Later, I tried it on the ship. The elf just fell off the ground because of GPS interference. I tried it several times, because the TV, telephone, Internet, etc. on the cruise ship all use satellite signals, which is particularly strong against the aircraft.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.